Hello all, I have installed Fedora Core2 (Kernel 2.6.5-1.358smp) on a system with Xeon MP processors. I ran the same program (multithreaded) on this system and compared the results Vs. what obtained on the same hardware running RH Advanced Server 3.0 (Kernel 2.4.21-9.ELsmp). Follows sar output: Linux 2.4.21-9.ELsmp (RH system) 06/17/2004 05:00:00 PM CPU %user %nice %system %idle 05:02:42 PM all 3.82 0.00 1.20 94.98 05:02:47 PM all 3.36 0.00 1.45 95.19 05:02:52 PM all 3.26 0.00 1.40 95.34 05:02:57 PM all 3.01 0.00 1.20 95.79 05:03:02 PM all 3.51 0.00 1.60 94.88 05:03:07 PM all 3.11 0.00 1.76 95.13 05:03:12 PM all 3.30 0.00 1.55 95.15 --------------------------------------------------------------------------------------- Linux 2.6.5-1.358smp (Fedora Core2 system) 06/17/2004 04:32:52 PM CPU %user %nice %system %iowait %idle 04:35:26 PM all 5.05 0.00 6.85 0.20 87.89 04:35:31 PM all 5.00 0.00 6.70 0.10 88.21 04:35:36 PM all 4.70 0.00 7.10 0.20 88.01 04:35:41 PM all 4.90 0.00 6.75 0.20 88.16 04:35:46 PM all 5.10 0.00 6.50 0.15 88.24 04:35:51 PM all 4.75 0.00 6.95 0.20 88.10 04:35:56 PM all 5.74 0.00 8.04 0.20 86.01 Both system time and user time are much higher on Fedora. Is it something you have already seen happening, or might just be related to kernel configuration ? Thanks to everybody will reply. In case I can provide more details/mesurements. One interesting thing is that the program is running even slower on Fedora. Regards Raffaele